IN-SITU BLOCKAGE MONITORING OF SENSING LINE

Abstract

Nuclear Power is expected to release low Green House Gas (GHG) emissions with very low impact upon climate change. It emits usually 6-10 g CO2/KWHe. Major share of nuclear power in energy mix can actively contribute in the reduction of GHG-emissions.It is considered that uranium cost is much lower, when compared fossil fuels.Nuclear power is inexpensive source of energy. Over the last 30 years, nuclear power plants around the globe have demonstrated their capacity and capability to produce base-load at affordable price. The nuclear power price does not fluctuate as of conventional fossil fuels. An other option for power generation are renewable energy sources which are under consideration in many countries around the world, but owing to their limited production capacity and weather dependency make their installation/operation at limited scale and their share in energy mix policy is very low. Uranium resources are widely distributed across the globe; however fossil fuel resources are accumulated in few regions of the world. It is very likely that uranium mining will not yield tensions and crisis among nations as it has been case for the gas and oil. Because of these factors, it is widely believed that nuclear power is a viable source of energy to meet future demands. There are pros and cons of nuclear power. Nuclear power plants (NPPs) requires strict monitoring of the physical parameters, e.g. Neutron flux, temperature of the reactor coolant, Reactor water level etc. If these parameters are not maintained within limits, than accident can erupt, which may cause release of radiations. Water level of reactor is an important parameter in NPPs. Reactor vessel level monitoring system, measures the water level in a reactor. Specific water level is crucially important for the protection of fuel. Drop in water level exposes the nuclear fuel, which may lead to fuel iii meltdown and radiation spread. This monitoring system mainly consists of sensing line and pressure transmitter. Sensing line extends from reactor vessel to pressure transmitter, which is installed outside the containment. Over a period of time Boron deposition or other impurities can cause sensing line blockage. Blockages of sensing line do not allow the accurate measurement of water level in reactor. The aim of our study is to determine the blockage in sensing line with energy of noise signal. This thesis simulates the blockages of sensing line with an equivalent pi circuit using electric-hydraulic analogy and examines the response of the system as blockage level is varied. Energy of noise signal is used to determine the occurrence of blockages. Noise signal extracted from the plant’s unblocked and blocked channels and simulation model is decomposed into high frequency components and low frequency component using wavelet filter bank. The signal is decomposed up to six levels. Percentage of energy is calculated at each level for low frequency components. It is observed that percentage of energy is being reduced as blockage level in sensing the line is increased. Based on the results it is safe to postulate results of simulation model and operational data are well correlated. Variation in percentage of energy can be used as indication to determine the occurrence of blockage in sensing line.